The invention relates to a device for adjusting a relative angular position of two rotating elements which are connected to a drive by a transmission element.
Devices of this type are used for example in internal combustion engines and are provided there for effecting a relative angular adjustment of the camshaft with respect to the crank-shaft driving the camshaft. The adjustments in the kinematics of the valve drive influences within limits the phase angle of the valve opening, the opening period and the valve stroke in a variable fashion.
DE 100 36 275 A1 discloses such a device for effecting a relative angular adjustment between a camshaft and a crankshaft of an internal combustion engine. A chain wheel is mounted on the camshaft so as to be driven by the crankshaft, the chain wheel driving the camshaft via a transmission element. The transmission element makes it possible to change the relative angular position of the two rotating elements, that is, the chain wheel and the camshaft. This change is brought about by an electric actuating drive whose rotor acts on an actuating shaft of the transmission element and which also rotates together with the camshaft in each operating state of the drive.
When inertia forces which are triggered by oscillations act on the rotor of the actuating element or the actuating shaft of the transmission element, undesired adjustments of the relative angular position may take place. This has to be compensated for by the actuating drive and requires a continuous application of energy. When the actuating drive fails, this function is no longer effective and uncontrolled adjustments occur which may make the operation of the internal combustion engine difficult and possibly damage the internal combustion engine. Since the actuating drive must also continuously rotate, it may also heat up during normal operation in an unacceptable way. In such a case, the internal combustion engine would have to be shut down in order to prevent damage to the actuating drive.
With respect to the general technical background, reference is made also to DE 100 38 354 A1 and DE 41 10 195 A1.
It is the object of the present invention to provide a device in which the actuating drive has a low electrical energy consumption and the device has a reliable emergency operating mode.